A citizen's group looking to improve Hillsborough County's transportation system has gathered more than enough signatures to qualify for November's ballot. But first, elections officials have to confirm that all the names on those petitions are valid.

More than 70,000 petitions were submitted as of Friday afternoon, says Gerri Kramer, spokeswoman for the Hillsborough County Supervisor of Elections office. So far, nearly one-third of those petitions they have reviewed were declared invalid. She says that can be because the person signing wasn't registered to vote, or is a duplicate name, for example. Elections officials have one month to verify the rest of the petitions. Backers need about 50,000 verified petitions to get it on the ballot.

The proposed referendum to the county charter would raise about $280 million per year through the sales tax hike starting in 2019. County commissioners refused to put the issue on the ballot in 2016, voting down the Go Hillsborough initiative. Hillsborough County voters also rejected a similar one-cent sales tax proposal in 2010.

Unlike the failed 2010 referendum, the proposed ballot measure would not allot money for specific transportation fixes like light rail or expanded bus service. It would instead give 45 percent of the funds raised to the Hillsborough Regional Transit Authority and the rest of the money to Hillsborough County, Tampa, Temple Terrace and Plant City. The agencies would then decide on what projects to fund, with guidance from the long-term transportation plan created by the Metropolitan Planning Organization.